Classification process and apparatus



1952 T. D. SHARPLES 3,015,391

CLASSIFICATION PROCESS AND APPARATUS Filed Feb. 24, 1960 5 SheetsSheet 17 35 52 INVENTOR.

THOMAS D. SHARPLES l4 BY/%GGW ATTORNEY Jan. 2, 1962 T. D. SHARPLES3,015,391

CLASSIFICATION PROCESS AND APPARATUS Filed Feb. 24, 1960 5 Sheets-Sheet2 INVEN TOR. THOMAS D. SHARPLES ATTOR N EY Jan. 2, 1962 T. D. SHARPLESCLASSIFICATION PROCESS AND APPARATUS 5 Sheets-Sheet 3 Filed Feb. 24,1960 -\-------------\\-\\&

INVENTOR. THOMAS D. SHARPLES ATTORNEY Jan. 2, 1962 T. D. SHARPLES3,015,391

CLASSIFICATION PROCESS AND APPARATUS Filed Feb. 24, 1960 5 Sheets-Sheet4 I03 I- a l I |0| lol 97 102 /5 Q u? 120 T m [6 IRS 16 .1 "1:1 |2|INVENTOR.

THOMAS D. SHARPLES ATTORNEY Jan. 2, 1962 T. D. SHARPLES CLASSIFICATIONPROCESS AND APPARATUS 5 Sheets$heet 5 Filed Feb. 24, 1960 INVENTOR.THOMAS D. SHARFfLES BY ATTORNEY United States Patent 3.915.391CLASSIFECATIQN PRGCESS AND APPARATUS Thomas D. Sharoles, PlymouthMeeting, Pa.. assignor to The Sharples Corporation. a corporation ofDelaware Filed Feb. 24', 196i). Ser. No. 10,596 14 Claims. (Cl. 209144)This invention pertains generally to the classification of finelydivided solids on the basis of size and density to produce fractions ofdifferent degrees of fineness, and pertains more particularly to animproved method and means for the control of fluid flow into theclassifying zone.

There are various types of classifiers that operate on the principle ofsubjecting finely divided solids, hereinafter referred to forconvenience as powder, to opposing forces comprised of an outwardlydirected centrifugal force and an inwardly directed drag force, thelatter resulting from the inward flow through the classification zone ofa fluid, e.g. liquid or gas, hereinafter referred to for con 'cnience indescription as air. In the operation of such classifiers, particleshaving a relatively lower ratio of surface area to mass, i.e. the largerparticles, are thrown outwardly by centrifugal force, whereas particleshaving a relatively higher ratio of surface area to mass, i.e. thesmaller particles, are carried inwardly by the air, the drag of the airon the smaller particles offsetting or overcoming the centrifugal forceimposed thereon.

The invention is particularly adapted for the control of the flow of airinto classifiers of the vortex type. In the operation of a vortexclassifier, air is introduced at the periphery of the classifying zone,and the direction of flow is controlled by mechanism, e.g. a volute orspaced vanes, so as to set up a spiral flow which proceeds inwardlythrough the classifying zone, the air leaving the classifying zonecentrally thereof. A particle introduced into the spiral flow, whetherat the periphery of the classifying zone or intermediate its inner andouter boundaries, will have a radially outward centrifugal force actingon it because of its tangential velocity, and a radial inward drag forceacting on it caused by the inwardly spiralling air.

The centrifugal force acting on the particle varies as the square of thetangential velocity whereas the radially inward drag force on theparticle varies directly with the radial component of air velocity.These forces for a particle of a given size are equal at some point inthe classifying zone of vortex classifiers generally, and at all pointsin the classifying zone, within at least practical approximation, inclassifiers of the type described and claimed in US. Patents 2,616,563and 2,796,173, and in co-pending application Serial No. 665,426, filedJune 13, 1957, now Patent 2,943,735.

From the foregoing it will be seen that, with all else remaining thesame including the velocity of inwardly flowing air, the greater thetangential velocity of air flow, the greater will be the centrifugalforce acting upon a particle carried along by that air flow, and sincethe centrifugal force varies as the square of the tangential velocity,whereas the drag force is directly proportional to the radially inwardflow of air, the smaller Will be the particles in the fine fraction.

it follows that, since classifying zones employed in vortex classifiersare annular in shape, the tangential component of air velocity in aspiral may be varied .between, as a maximum, the tangential introductionof the inwardly flowing air into the annular classifying zone, and, as aminimum, the direct radial introduction of the incoming air.

Thus in the case of any given classifier operating on the vortexprinciple, irrespective of design and construc- Patented Jan. 2, 1962"ice tion, and with the same volume of incoming air, the nature of thetwo fractions may be varied, the fine fraction being generally finer orcoarser depending upon the angle from tangential to radial that theincoming air enters the classifying zone.

In classifiers of commercial design, the direction of air fiow into aclassifying zone is customarily controlled by vanes which may beadjustable or fixed. In the case of adjustable vanes, constructiondifficulties are such as to greatly increase the cost of manufacture. Inthe case of classifiers with fixed vanes on the other hand, in order tovary the direction of air fiow into the classifying zone it is necessaryto manufacture replaceable units, each having vanes positioned at adiiferent angle from that of the other units. A set of suchinterchangeable units, while less expensive to manufacture, have limitedutility because of necessity they must be limited in number. Then too,no adjustment as to air angle can be made while the machine is inoperation.

The present invention is directed to the control of the angle ofintroduction of air into an annular classifying zone which is highlyversatile in that any desired angle may be obtained quickly and easilywith apparatus of relatively low cost of manufacture.

In the practice of the invention, the infiowing air is introduced intothe classifying zone in a plurality of directions, hereinafter referredto, for convenience, as angles, the direction tangential to theclassifying zone being regarded as of zero angle, and the directionradially inwardly of the classifying Zone being regarded as of angle.Thus when air streams of two di erent angles are employed, one may betangential and the other radial to obtain the desired resultant angle ofentry of air into the classifying zone through adjustment of thevelocity and volume of the two component flows with respect to eachother. On the other hand, the two component air flows may be directedinto the classifying zone at any other two difierent angles between thezero or tangential angle and the plus 90 or radially inward angle, i.e.the angle which a line directed radially inwardly defines with respectto the tangential line. The angle which a radially outwardly directedline defines with respect to the tangential line, in light of theforegoing explanation, would have a value of minus 90.

Further features of the invention will become apparent to personsskilled in the art as the specification proceeds in connection with theaccompanying drawings in which:

FIGURE 1 is an elevation partly in section of an embodiment of theinvention;

FIGURE 2 is an enlarged section shown broken of'a left-hand portion ofFIGURE 1;

FIGURE 3 is an enlarged section shown broken of a right-hand portion ofFIGURE 1;

FIGURE 4- is a view shown broken taken on line P4 of FIGURE 1;

FIGURE 5 is a plan view shown broken of vane adjusting mechanism;

FIGURE 6 is an exploded view of vane rings;

FlGURES 7, 8, 9 and 10 show the air control vanes in difierent adjustedpositions with respect to each other, being views partly in sectiontaken on lines 77, 8-8, 9-9, and 1010 of FIGURE 4;

FIGURE 11 is an elevation shown broken and largely in sectionillustrating another embodiment of the invention;

FIGURE 12 is a view taken on line 1212 of FIG- URE 11;

FIGURE 13 is an elevation shown broken of the vane rings of FIGURES l1and 12;

FIGURE 14 is an elevation shown broken and largely in section of afurther embodimentof the invention;

FIGURE 15 is a plan view shown broken taken on line 15-15 of FIGURE 14;

FIGURE 16 is a View taken on line 16-16 of FIG- URE 14;

FIGURE 17 is an elevation shown broken and largely in section of a stillfurther embodiment of the invention;

FIGURE 18 is a section shown broken of an air inlet of FIGURE 17 indifferent adjusted position;

FIGURE 19 is a view shown broken on line 19-19 of FIGURE 17; and

FIGURE 20 is a view shown broken and largely in section of an additionalembodiment of the invention.

Referring now more particularly to FIGURES 1 to 3, note is made of thefact that the method and means shown and described herein for feedingpowder into the classifying zone are more particularly described andclaimed in my co-pending application Serial No. 10,762, filed of evendate herewith. At is shown a base or support upon which is mounted acylindrical casing 11 having an inwardly projecting upper rim 12 whichsupports and to which is attached, e.g. by welding, an annularring 13having a rounded inner circular edge 14 which functions as the inneredge of an annular classifying zone 17. Resting upon and attached toring 13, e.g. by bolts or screws, is an annular structural member 15shown as having a flat inner bottom surface which serves as the lowerend surface or wall of classifying zone 17.

. The inner bottom and side wall of member 15 is shown lined withwear-resisting material, illustrated at 16, which may be of ceramictile, e.g. of tungsten carbide, cemented in position.

Since the various parts may be secured together in any desired manner,such as by bolts, screws, Welding and the like, the particular manner ofattaching parts to one another for purposes of brevity, will ordinarilynot be referred to.

Member 15 has an upwardly projecting annular portion 18 which supportsannular member 19 attached thereto.

Projecting inwardly from member 19 are a plurality of circumferentiallyspaced pins 20 which project into and support an annular plate 21, thespacing between member 19 and plate 21 being such as to provide anannular inlet 22 leading to classifying zone 17, said inlet containing apair of cooperating air directing vane rings 23 to be hereinafter moreparticularly described, since it is to the generic and specific featuresinvolved that this invention is directed.

Resting upon and secured to plate 21 is a cylindrical support 24 forfeed funnel 25 having a downwardly projecting feed tube 26 surrounded byfiller members 27 and 28.

Positioned within casing 11, and encased within an interior casing 30,is housing 31 in which is journaled, in bearings not shown, a spindle 32having a pulley 33 attached to'its lower end. Mounted on the upper endof spindle 32 is a circular plate 34 shown shaped about its peripheralunder portion in a manner to define a surface of revolution 35 of curvedcross section, i.e. a surface generated by revolving a curved line,having a shape as illustrated, around the axis of the machine. Surface35 which, as illustrated, is rotatable, comprises the inner part of theupper end surface or wall of the classifying zone. The rest of the upperend surface or wall is supplied by surface 36 on ring 37, the latterbeing attached to the under surface of plate 21, as illustrated at 38.Surface '36 also is asurface of'revolution.

Positioned on top of plate 34 is an annular member 41 which is providedwith a plurality of circumferentially spaced radial channels 42,preferably lined with wear-resistant tubes, e.g. ceramic tubes, say oftungsten carbide, as illustrated at 43. Superimposed upon member 41 isan annular member 44 secured to plate 34 by any desired means, such asby circumferentially spaced screws as illustrated at 45, thus holdingmember 41 in position. Member 44 has an inwardly projecting innercircular edge which together with the upper central portion of plate 34forms a powder feed chamber 47, plate 34, as shown, being provided witha central wear-resistant disc 48, e.g. of tungsten carbide, resting upona somewhat larger disc provided at the center of plate 34. It will benoted that feed tube 26 leads into feed chamber 47, and that radialchannels 42 lead outwardly from feed chamber 47. It will also be notedthat plate 34, members 41 and 44, spindle 32, and pulley 33 are joinedtogether and comprise the rotor, whereas the rest of the parts remainstationary.

Spaced radially outwardly from the outer ends of channels 42 in a mannerto form an annular gap 51 is a wear ring 52 mounted on ring 37. Ring 52is so positioned with respect to channels 42 as to intercept the powderfed outwardly through channels 42 upon rotation of the rotor.

While the surface of ring 52' facing gap 51 may be made parallel to theouter periphery of the rotor which in turn may be made parallel to theaxis of rotation of the rotor, it is preferred, and as described andclaimed in my above-mentioned co-pending application, that such innersurface 55 of ring 52, quite apart from the shape of the'outer peripheryof the rotor, define an angle a with respect to the axis of rotation ofbetween 5 and 15 for highly efiicient delivery of the powder intoclassifying zone 17, although values of angle a up to but less than 45are contemplated, i.e. directions of lateral flow into the classifyingzone in which the axial component exceeds the radial component. Ring 52is preferably wear-resistant, and conveniently may be of ceramic tile,

e.g. of tungsten carbide, cemented in position on ring 37.

Any desired means may be employed for effecting the flow of air throughclassifying zone 17 inwardly through annular irflet 22, and outwardlythrough annular chamber 56 between casing 11 and casing 30, e.g. blower57 positioned in conduit 58, the latter leading from bag filter 59 inwhich the fine fraction is collected, filter 59 being connected tochamber 56 by conduit 60.

In the operation of the classifier shown in FIGURES 1 to 3, upon thefunctioning of blower 57, fluid, such as air, flows into annular inlet22 and acquires an inwardly spiralling flow by virtue of the functioningof vane rings 23 to be hereinafter more particularly described, saidvane arrangement affording the desired shape to the spiralling flow.

The unitary structure comprised of spindle 32 and the parts mountedthereon being in rotation, the powder is fed into chamber 47 throughfunnel 25 and pipe 26. From chamber 47 the powder flows outwardlythrough channels 42, thereby acquiring a rotary motion, and is projectedagainst ring 52. The relative rotational movement between member 41 andring 52 develops a relatively high degree of sheer in the powder todeagglomerate any agglomerated particles present, and also uniformlydistribute the powder circumferentially in gap 51 from which the powderenters annular classifying zone -17 laterally thereof, in the form of arotating annulus comprised of substantially uniformly distributedpowder.

The rotation of the annulus of powder entering classifying zone 17 is inthe same direction as that of the spiralling air, and for best resultsthe speed of rotation of powder and the speed of rotation of the air atthe place or circular area of entry of powder laterally into the air arepreferably substantially evenly matched at least within practicalapproximation.

The powder, upon laterally entering the inwardly spiralling flow of air,is acted upon by the centrifugal force resulting from its rotation, andalso by the radial component of flow of air through the classifyingzone. The result is that the larger particles, having a relatively lowerratio of surface area to mass, are thrown outwardly by centrifugalforce, whereas the smaller particles having a relatively higher ratio ofsurface area to mass, are carried inwardly by the inwardly spirallingair.

The air, bearing the fine fraction, after passing around circular edge14, enters annular chamber 56, and passes out through filter 59 whereinthe fine fraction is collected, the air, free from fines, passing outthrough blower 57.

The coarse fraction, being thrown outwardly in rotating condition,slides around the inner periphery of member and passes out through atangential opening 61 leading into a circular chamber 62 from which itis withdrawn through outlet 63.

Classifying zone 17 may be of any desired shape with end surfaces orwalls stationary or rotating, or stationary in part and rotating inpart, such as those more particularly described and claimed in U.S.Patents 2,616,563 and 2,796,173, and in co-pending application SerialNo. 665,426, filed June 13, 1957, now Patent 2,943,735. The invention,however, is particularly suitable for use wit classifying zones adaptedfor free vortex flow of inwardly spiralling fluid. In the preferredclassifying zone, the axial distance, designated for convenience h,between the opposing end surfaces or walls at any radial distance,designated for convenience r, from the axis of rotation bears, within atleast practical approximation, the following relationship:

where h is the axial spacing between the end surfaces or Walls at theouter boundary of the classifying zone, and r is the radius from theaxis of rotation to the outer boundary of the classifying zone.

Classifying zone 17 is considered as having an outer periphery beginningat an imaginary circular line 64 on surface 36 and an inner periphery atcircular edge 14, and even though the lower end surface or wall may befiat, its spacing with respect to surfaces 35 and 36, in the preferredembodiment, conforms within practical approximation to the aboveequation, the feed of powder into the classifying zone beingintermediate its inner and outer boundaries.

It is to be understood, however, that the classifying Zone may have anyother shape and that the point or area of feed of powder may beintermediate the inner and outer boundaries of the classifying zone asillustrated, or outwardly from the outer boundary thereof, or otherwise,as desired.

A multiplicity of methods and means may be provided for carrying out theinvention of the present application, and various alternatives areillustrated in the drawings.

Referring now more particularly to FIGURES 4 to 10, as well as toFIGURES 1 to 3, it will be noted that vane rings 23 are comprised ofupper ring 71 and lower ring 72, the former superimposed upon the latterwith their inner peripheral edges positioned in an annular groove 73 inring 37, said groove being positioned directly under plate 21. Ring 72is held against rotation by means of a pin 74 secured in plate 21 andwhich extends downwardly into bore 75 positioned in the inner edge ofring 72, pin 74 passing through a longitudinal notch 76 in ring 71.Notch 76 is of sufiicient length to permit rotational movement of ring71 with respect to ring 72 for purposes to he hereinafter moreparticularly described.

To facilitate rotational movement of ring 71 with respect to ring 72,ring 72 is provided with a plurality of circumferentially spaced notches77, each of which is provided with a spring member 78 which pressesagainst ring 71 tending to spread the rings apart. After the desiredadjustment of ring 71.with respect to ring 72 is made, the rings areheld in adjusted position by the tightening of a pluraiity ofcircumferentially spaced screws, one screw being illustrated at 81 inFIGURE 2. The tightening of screws 31 compresses spring 78 and securesrings 71 and 72 together.

To facilitate the movement of ring 71 with respect to ring 72, ring 71may be provided with handle 82 which passes downwardly through alongitudinal notch 83 in 6 plate 21, better seen in FIGURE 4. Ifdesired, a fixed gauge member 84 may be secured to plate 21, the distance from edge 85 of which to edge 86 on handle 82 may be utilized asan indicator of the rotational position of ring 71 with respect to ring72. A set of gauge blocks of different widths for insertion betweenedges 85 and 86, each gauge block indicating a different relativerotational position of ring 71 with respect to ring 72, is very usefulfor the purpose.

That portion of ring 72 which is positioned in annular inlet 22 isprovided with two sets of circumferentially spaced grooves or slots, oneset of grooves 37 being of greater angle with respect to the axis of theclassifying zone than the second set of grooves 88. If desired, grooves87 may be so positioned as to direct incoming air passing therethroughtangentially with respect to the classifying zone, whereas the grooves38 may be so positioned as to direct incoming air radially into theclassifying zone. On the other hand, grooves 87 and 88 may direct theincoming air in any other desired different directions into theclassifying zone, e.g. between the tangential and radial directions.-The use of the tangential direction for one set of grooves and theradial direction for the other set of grooves provides a high degree ofversatility in obtaining the desired resultant direction of air flowinto the classifying zone.

From what has been said, it will be seen that ring 72 may be employedindependently of ring 71 in the practice of the invention, in which casethe resultant direction of air flow would be fixed, no adjustment beingprovided, except by making ring 72 interchangeable. For purposes ofversatility, therefore, the use of ring 71, having a plurality ofcircumferentially spaced shutter members 91, is preferred.

Shutter members 91 preferably have the shape com parable to thatindicated in FEGURE 7, for when in the position shown grooves 87 and 88are fully open, the ends of shutter members 91 being shapedappropriately for the purpose.

When ring 71 is shifted to the position shown in FIG- URE 8, grooves 87are left fully open but grooves 83 are partially closed, the result ofwhich is that the resultant direction of air how is shifted toward thetangential.

When ring 71 occupies the position shown in FIG- URE 9, grooves 88 arecompletely closed, and the resultant direction of air flow into theclassifying zone has been shifted the maximum amount, with the groovesin question, toward the tangential.

In FIGURE 16 ring 71 is illustrated in a position in which grooves 87are completely closed, leaving grooves 88 for the most partunobstructed. With the shutter blocks 91 in the position shown in FIGURE10, the resultant direction of air flow into the classifying zone ismoved the maximum amount toward the radial that is possible with theparticular vane rings illustrated. It will be recognized that a lessershift of ring 71 clockwise in FEGURE 10 would leave grooves 87 partiallyopen, the degree to which being adjustable by movement of ring 71.

From the foregoing it will be seen that shutter blocks 91 may be soshaped and positioned with respect to grooves 87 and 88 as to obtain anydesired resuitan; direction of, air flow into the classifying zones.

Another embodiment of the invention is shown in F 1G- URES 11 to 13wherein the air entering classifying zone 92 is fed downwardly throughan annular space 93 between spaced concentric walls 94 and 95, theresultant angle of flow being controlled by vane rings 96 and 97, theformer being movable and the latter remaining stationary. The feed ofpowder into classifying zone 92 is through a feed tube 98, and the airleaves the classifying zone centrally thereof up through a tube 99, thestructure being as indicated.

Stationary ring 97 as seen in FIGURES l2 and 13 is provided with aseries of diagonal grooves 101 and a series of transverse grooves 102.

Air passing downwardly through grooves 101 has imparted to it acircumferential component of flow which has a tangential component withrespect to the classifying zone 92, whereas air passing down throughgrooves 102 has imparted to it a longitudinal component of flow which isradial with respect to the classifying zone 92. The resultant of the twoflows determines the angle at which the spiralling flow enters theclassifying zone 92, analogous for all purposes to the resultant or airflows through grooves 87 and 88 as above described.

While stationary ring 97 may be employed alone in the practice of theinvention, it is preferred to provide adjustment such as by vane ring 96which is provided with a plurality of circumferentially spaced shutterblocks 103. For adjustment purposes ring 96 is pro vided with a handle"104 which passes through longitudinal slot 105 in shell 94 and engagesone shutter block 103 as illustrated.

Assuming that grooves 101 and 102 are both closed by shutter blocks 103,movement of shutter blocks 103 to the right as seen in FIGURE 13 wouldgradually open grooves 101 to permit diagonal flow of air through ring97. Further movement of shutter blocks 103 to the right would graduallyuncover grooves 102 to permit longitudinal flow of air through ring 97along with the diagonal flow through grooves 101. The reverse order ofopening of grooves 101 and 102 would occur upon movement of shutterblocks 1103 to the left. Thus the desired relative flows may be obtainedby adjustment of the relative rotational position of ring 96 withrespect to ring 97.

Another embodiment of the invention is illustrated in FIGURES 14 to 16wherein air flow into classifying zone 106 is controlled by vane rings107 and 108.

Vane ring 107 is provided with blocks 111 which mesh with blocks 1 12 onvane ring 108, the spacing of blocks 111 and 112 with respect to eachother being such that, when in the position shown in FIGURE 16, aplurality of circumferentially spaced diagonal channels or grooves 113and a plurality of circumferentially spaced radial channels or grooves114 are provided.

As shown, vane ring 108 is fixed, and vane ring 107 is made adjustablycircumferentially to move blocks 111 counterclockwise as seen in FIGURE16 to narrow or close channels 114 and at the same time enlarge channels113. On the other hand, movement of blocks 111 clockwise as seen inFIGURE 16 narrows or closes channels 113 while at the same timeenlarging channels 114. Thus the volume of diagonal (less angular) flowwith respect to the volume of radial (more angular) flow is madeadjustable to arrive at the desired final resultant flow of air intoclassifying zone 106.

Movement of vane ring .107 is accomplished by lossening screws 115 whichpass down through longitudinal slots 116 in top plate 117. A two-partvernier scale 118 may be provided if desired to indicate the relativeposition of vane rings 107 and 108 with respect to each other, part 119being fixed to plate 117 and part 120 being movable with screws 115which engage vane ring 107. When the desired adjustment is obtainedscrews 115 are tightened to hold vane rings 107 and 108 in the desiredadjusted position.

Flow of air into classifying zone 106 is inwardly through annularchamber 121 which surrounds vane rings 107 and 108, the flow being tothe left as seen in FIG- URE 14, the air picking up the desiredspiralling flow upon passage through channels 113 and/or 114.

Feed of powder intoclassifying zone 106 is through feed pipe 122 and aplurality of circumferentially spaced radial channels 123 positioned inrotating plate 124. In

the particular classifier of FIGURE 14, bottom plate 125 also rotates.The inwardly spiralling air carrying the fine fraction therewith leavesclassifying zone 106 through annular opening 126, and the heavy tractionafter being thrown outwardly drops down through outlet 127.

Another embodiment of the invention is shown in FIGURES 17 to 19,wherein the circumferential air inlet structure shown at 131 and leadinginto classification zone 132 (shown broken) is comprised of two branches133 and 134, each set at an angle with respect to classifying zone 132.

Air inlet structure 131 and its branches 133 and 13d surroundclassifying zone 132 which may be annularly shaped, e.g. as in Patent2,796,173.

Each branch 133 and 134 has an annular air inlet 135 which is borderedon each of opposite sides with an inwardly extending annular groovedmember 136, the grooves being diagonal as illustrated at 137 in FIGURE19.

Secured to the face of one grooved member 136 of each pair, such as bythe use of a suitable cement, is a flexible tube 138, e.g. of rubber,natural or synthetic, which is inflatable much the same as the tube ofan automobile tire. Tube 138 is shown deflated in FIG- URE 17 to providea gap 141 between opposed members 136, and inflated in FIGURE 18 toclose gap 141. It is understood that tube 138 extends completely aroundits associated member 136 so as to be endless and completely circular.

In the operation of the embodiment shown in FIG- URES 17 to 19, airdrawn into inlet 135 has a diagonal component of flow imparted to itupon passing through grooves 137, and a longitudinal or radial componentof flow upon passing through gaps 141, the maximum longitudinal orradial flow occurring when tube 138 is completely deflated. Thelongitudinal or radial component of flow decreases with increase ininflation of tube 138 until such time that tube 138 is suflicientlyinflated to completely close gaps 141 as illustrated in FIGURE 18. Flowthrough grooves 137 continues at all times. Thus the resultant of airflow is variable at Means for inflating and deflating tubes 13% isillustrated in FIGURE 17 as being comprised of tubes 142 connected to asource of air not shown, the entrance and exit of air being controlledby a valve or a pressure regulator 143. A gauge 144 might be provided inair supply line 145 to be used as a guide in the inflation and deflationof tubes 138.

A still further embodiment of the invention is illustrated in FIGURE 20in which 146 is a stationary casing having an annular air inlet 147 inwhich is positioned a plurality of circumferentially spaced diagonalvanes 148 which impart a rotary or diagonal movement to the air uponentering classifying chamber 150. An annular opening 151 in which isdisposed a circular tube 152 permits air to enter longitudinally orradially, the volume of the last-mentioned air being controlled byinflating or deflating tube 152. It will be understood that uponcomplete inflation of tube 152, gap 153 is closed, and that uponcomplete deflation of tube 152, gap 153 is open to its greatest extent.It will be obvious that any intermediate opening of gap 153 may beobtained upon control of the inflation of tube 152 to vary the resultantof air flow at will.

154 is a rotor which may be much the same as that illustrated in FIGURE1, powder to be classified being delivered through a plurality ofoutwardly extending tubes 155, the powder striking surface 156 to bedelivered into the classifying zone much the same as already describedin connection with FIGURES 1 to 3.

Experiments with classifiers embodying the invention cogentlydemonstrate the outstanding contribution to the art that has been made,it being possible to adjust the resultant angular entry of the inwardlyflowing spiral of air into the classifying zone at will with excellentprecision and with the classifier in full operation. This is of veryconsiderable advantage for it makes possible 9 variation in air flowwhile observing the classifying operation and to immediately adjust inaccordance with the desired results.

As has been brought out above, the invention is applicable toclassifiers and classifying operations without limitation in which aninwardly spiralling flow of fluid, whether or liquid or gas, e.g. ofwater or air, takes place. The construction and operation of vortexclassifiers in general, whether employing liquid or gas as a medium, arein a rather highly developed state, to which this invention makes amajor contribution. Several embodiments of the invention have been shownand described, and others will occur to persons skilled in the art uponbecoming familiar herewith. For instance, the resultant angle of thespiral may be varied, i.e. moved toward the tangential by the peripheralapplication of reduced pressure between any of the various multiple airdirecting means shown and described and the classifying zone, or othermeans for accomplishing such purpose may be devised. Also, the inwardlyflowing fluid may be directed inwardly toward the classifying zone atany other desired number of angles, e.g. three or four, if desired forany reason, to obtain the desired resultant of air flow, as will becomeobvious to persons skilled in the art upon becoming familiar with theabove description. Wear-resistant material may be placed at any point ofwear and While reference has been made to tungsten carbide, othermaterials act excellently, e.g. the ceramic aluminum oxide.

it is, therefore, to be understood that the above particular descriptionis by way of illustration and not of limitation, and that changes,omissions, additions, sub stitutions and/ or other modifications may bemade without departing from the spirit of the invention. Accordingly, itis intended that the patent shall cover, by suitable expression in theclaims, the various features of patentable novelty that reside in theinvention.

I claim:

1. The method of classifying finely divided material on the basis ofsize and density which comprises directing a fluid in a plurality ofdirections toward an annular classifying zone positioned between spacedwalls to bring the body of fluid between said walls into an inwardlyspiralling flow, one of said directions relative to said classifyingzone being different from that of another of said directions, feedingsaid finely divided material into said classifying zone forclassification therein, withdrawing from an inner boundary of said zonea fine fraction of said finely divided material, withdrawing from theperiphcry of said zone a coarse fraction of said finely dividedmaterial, and controlling the volume of the component fluid flows withrespect to each other to obtain the desired shape of the spiral in theinwardly spiralling flow.

2. The process of claim 1 in which the inward spiral flow of said air isin the form of a free vortex.

3. The process of claim 1 in which the ends of said classifying zone areat least in part rotating, and in which said spiral rotates in the samedirection.

4. The process of claim 1 in which said finely divided particles are fedinto the inwardly spiralling flow while rotating in the same directionand within practical approximation at a matched speed of rotation.

5. Theprocess of claim 3 in which said finely divided particles are fedinto the inwardly spiralling flow while rotating in the same directionand within practical approximation at a matched speed of rotation.

6. A classifier for finely divided material comprising boundary meansincluding first and second opposing wall structures forming between theman annular classifying zone, inlet means including a plurality offluid-directing means adjacent the outer limit of said zone forproducing within said zone an inwardly spiralling vortex, one saidfluid-directing means directing fluid in a direction relative to saidclassifying zone which is different from that of another saidfluid-directing means, inlet means for said finely divided material,outlet means communicating with the inner boundary of said annularclassifying zone, means for producing a differential in pressure betweensaid first-mentioned inlet means and said outlet means for the flow offluid into said classifying zone directed by said plurality offluid-directing means and out of said classifying zone through saidoutlet means, and means for controlling the volume of the componentfluid flows with respect to each other to obtain the desired shape ofthe spiral in the inwardly spiralling flow.

7. The combination of claim 6 which includes means for adjusting thefluid-directing magnitude of the plurality of fluid-directing means withrespect to each other.

8. The combination of claim 7 in which the means for adjusting therelative magnitude of said fluid flows takes the form of grooved ringsmovable relative to each other.

9. The classifier of claim 6 in which the axial distance h between theopposing wall structures of the classifying zone at any radial distancer from the axis of rotation bears within practical approximation thefollowing relationship:

where h is the axial spacing between the wall structures at the outerboundary of the classifying zone and r is the radius from the axis ofrotation to the outer boundary of the classifying zone.

10. The method of classifying finely divided material on the basis ofsize and density which comprises directing air in a plurality ofdirections toward an annular classifying zone positioned between spacedwalls to bring the body of air between said walls into an inwardlyspiralling flow, one of said directions relative to said classifyingzone being more tangential than radial and another of said directionsrelative to said classifying zone being more radial than tangential,feeding said finely divided material into said classifying zone forclassification therein, withdrawing fr'om an inner boundary of said zonea fine fraction of said finely divided material, withdrawing from theperiphery of said zone a coarse fraction of said finely dividedmaterial, and controlling the velocity and volume of the component fluidflows with respect to each other to obtain the desired shape of thespiral in the inwardly spiralling flow.

11. A classifier for finely divided material comprising boundary meansincluding first and second opposing wall structures forming between theman annular classifying zone, inlet means including fluid-directingmembers adja cent the outer limit of said zone for producing within saidzone an inwardly spiralling vortex, said fluid-directing members beingdivided into at least two groups with the members of one said groupbeing inter-spersed between members of another said group and with thefluid-directing members of said one group having means for directingfluid in a direction relative to said classifying zone which isdifferent from that of said another group, inlet means for said finelydivided material, outlet means communicating with the inner boundary ofsaid annular classifying zone, means for producing a differential inpressure between said first-mentioned inlet means and said outlet meansfor the flow of fluid into said classifying zone directed by saidfluid-directing members and out of said classifying zone through saidoutlet means, and means for controlling the volume of the componentfluid flows with respect to each other to obtain the desired shape ofthe spiral in the inwardly spiralling flow.

12. A classifier for finely divided material comprising boundary meansincluding first and second opposing wall structures forming between theman annular classifying zone, inlet means including a plurality offluid-directing means adjacent the outer limit of said zone forproducing within said zone an inwardly spiralling vortex, one saidfluid-directing means directing fluid in a direction relative to saidclassifying zone which is different from that of another saidfluid-directing means, inlet means for said finely divided materialcarried byione of said wall structures and extending into communicationwith said zone at a feed point intermediate its inner and outer limits,saidiboundary means being in part stationary and in part rotatable, saidrotatable part including said inlet means, means for feeding finelydivided material to said lastmentioned inlet means, means for drivingsaid rotatable part, outlet means communicating with the inner boundaryof said annular classifying zone, means for producing a differential inpressure between said firstmentioned inlet means and said outlet meansfor the flow of fluid into said classifying zone directed by saidplurality of fluid-directing means and out of said classifying zonetogether with a fine fraction through said outlet means, outlet meansfor a coarse fraction communicating with the outer boundary of saidannular classifying zone, and means for controlling the volume of thecomponent fluid flows with respect to each other to obtain the desiredshape of the spiral in the inwardly spiralling flow.

13. A classifier for finely'divided material comprising boundary meansincluding first and second opposing Wall structures forming between theman annular classifying zone, inlet means including a plurality offluid-directing means adjacent the outer limit of said zone forproducing within said zone an inwardly spiralling vortex, one saidfluid-directing means directing fluid in a direction relative to saidclassifying zone which is dilferent from that of another saidfluid-directing means, inlet means for said finely divided materialcarried by one of said wall structures and extending into communicationwith said zone at a feed point intermediate its inner and outer limits,said boundary means including said inlet means being rotatable, meansfor feeding finely divided material to said lastmentioned inlet means,means for rotating said boundary means, outlet means communicating withthe inner boundary of said annular classifying zone, means for producinga differential in pressure between said firstmentioned inlet means andsaid outlet means for the flow of fluid into said classifying zonedirected by said plurality of fluid-directing means and out of saidclassifying 12 zone together with a fine fraction through said outletmeans, outlet means for a coarse fraction communicating with the outerboundary of said annular classifying zone, and means for controlling thevolume of the component fluid flows with respect to each other to obtainthe desired shape of the spiral in the inwardly spiralling flow.

14. A classifier for finely divided material comprising boundary meansincluding first and second opposing wall structures forming between theman annular classifying zone, inlet means including a plurality offluid-directing means adjacent the outer limit of said zone forproducing within said zone an inwardly spiralling vortex, one saidfluid-directing means directing fluid in a direction relative to saidclassifying zone which'is different from that of another saidfluid-directing means, inlet means for said finely divided materialcarried by one of said wall structures and extending into communicationwith said zone at a feed point intermediate its inner and outer limits,said boundary means being stationary, means for feeding finely dividedmaterial to said last-mentioned inlet means, outlet means communicatingwith the inner boundary of said annular classifying zone, means forproducing a differential in pressure between said firstmentioned inletmeans and said outlet means for the flow of fluid into said classifyingzone directed by said plurality of fluid-directing means and out of saidclassifying zone together with a fine fraction through said outletmeans, outlet means for a coarse fraction communicating with the outerboundary of said annular classifying zone, and means for controlling thevolume of the component fluid flows with respect to each other to obtainthe desired shape of the spiral in the inwardly spiralling fiow.

References Cited in the file of this patent UNITED STATES PATENTS

